1. Field of the Invention
This invention relates to a multi-storey building and a method of construction thereof wherein the building is constructed using insulated concrete forms. More particularly, this invention relates to buildings exceeding three stories.
2. Description of the Prior Art
Insulated concrete form (ICF) buildings have generally not been constructed with more than three stories because the building code requirements cannot be met in a cost effective manner. Also, great difficulty has been encountered in keeping the ICF walls sufficiently straight. As can be appreciated, it is difficult to keep the ICF walls straight as the concrete is being poured because the foam walls of the forms are lightweight and are preferably not supported by external supports. With some ICF buildings, the foam walls are supported by supplementary supports to keep the walls reasonably straight while the concrete is poured. The supplementary supports are located against the outer side surfaces of the inside and outside foam layers and are usually anchored to the ground. For example plywood supplementary supports are held against the outer side surfaces of the foam layers by wooden boards (e.g. 2×4's) that are anchored on the ground and extend at an angle. After the concrete has set, the supplementary supports, which are used on both the outside and inside foam walls, are removed. Also, the concrete is extremely heavy compared to the weight of the forms. For buildings of three stories or less, if the first wall for example, is not straight within a particular narrow tolerance, then the wall for the second storey will be more out of line and the wall for the third storey will be even further out of line. As can be appreciated, if there are four stories or eight stories or more in the building, the mistakes made on the lower floors are compounded to a point where the walls on the upper stories would be noticeably out of line. Supplementary supports are expensive and time consuming to install and remove. Also, supplementary supports are even more expensive and labour intensive on upper storeys of multi-storey buildings. For example, in some ICF buildings, the first storey of foam forms are supported inside and outside by supplementary supports that are anchored in the ground and extend at an angle to the foam forms. It is not cost effective to have removable supplementary supports in high rise buildings. It is not feasible to use supplementary forms that extend up from the ground in buildings exceeding three stories. It is extremely expensive, if not impossible, to correct an upper storey ICF wall on a high-rise building that is out of line. Repairs must be made to the outside surface of the misaligned wall from the outside of the building. Often an outer portion of the concrete wall must be removed in an attempt to straighten the wall as much as possible.
ICF buildings can be constructed having a masonry exterior. However, since the forms themselves are very expensive compared to other concrete forms, it becomes extremely expensive to add a masonry or brick exterior to an ICF building. ICF buildings can be cost competitive when the exterior surface of the building is a type of stucco. Many jurisdictions have fire regulations that become more stringent when buildings exceed three stories. In the Province of Ontario, Canada, for example, there is a building code requirement that provides that exterior cladding on a building must remain in place for the minimum time required by the code from the commencement of the fire. The purpose of this regulation is to prevent the exterior cladding of the building from falling onto people who are attempting to escape from the building or from falling onto fire personnel. With ICF buildings completed with a stucco exterior, the exterior foam layer can fall off the building during a fire. If a building will not meet the fire regulations in the jurisdiction where the building is to be constructed, no building permit will be issued. Further, insurers are not willing to insure any building that does satisfy all of the fire regulations.
Insulated concrete forms are known. The form walls are separated by a predetermined distance by ties that are embedded in the foam. Most forms are designed to construct vertical walls at a 90° angle relative to one another. Some forms are angled to construct walls at a 45° angle to one another. Other forms are curved to allow curved walls to be constructed. Forms are specifically designed for use as corner forms. One ICF manufacturer is Nudura (a trademark). The Nudura forms have hinged ties so that the parallel foam walls can be collapsed together during transport and separated during use. The Nudura forms have a standard size of 8 feet by 1.5 feet and are made from expanded polystyrene foam with hinged polypropylene ties. The polystyrene foam is stated to have a density of 1.26 lbs/ft3, a flame spread index of less than 75 and a maximum smoke development index of less than 450 when tested under UL723. Nudura and other manufacturers produce numerous accessory forms. Insulated concrete forms can provide the formwork for foundation and basement load bearing walls and interior or exterior load bearing walls. Of course, ICF can be used on non-load bearing walls as well.
While it is common to construct ICF buildings up to three stories, buildings beyond three stories have generally not been constructed using insulated concrete forms. Free standing ICF buildings beyond three stories have not been constructed previously. An advantage of having an ICF building is that the completed building has a monolithic poured concrete wall installed between the two foam layers of the insulated concrete forms. Voids within the concrete are removed using agitators just after the concrete is poured. The foam layers provide the insulation for the building. Thus, the building is solidly constructed and it is well insulated making it less expensive to heat in the winter and less expensive to aircondition in the summer. The disadvantage is that the insulated concrete forms themselves are expensive relative to other types of construction.